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NASA NTRS2019

Pixel Based Model for High Latitude Dust Detection

High Latitude Dust (HLD, ≥ 50°𝑁 𝑎𝑛𝑑 ≥ 40°𝑆 ) load has implications on the energy budget, ocean biodiversity and economy on a regional and global scale. Current methods of dust detection rely on spectral sensitivity at visible (RGB) and infrared wavelengths. The characteristics of HLD vary according to the sediments and sedimentary processes operating on the land surface that are the source of the dust particles. Leveraging machine learning (ML) methods, we propose a new detection method based on convolutional neural network (CNN) using true color images.

Priftis, Georgios↗
NASA NTRS2022

Newly Identified Climatically and Environmentally Significant High-Latitude Dust Sources

Dust particles from high latitudes have a potentially large local, regional, and global significance to climate and the environment as short-lived climate forcers, air pollutants, and nutrient sources. Identifying the locations of local dust sources and their emission, transport, and deposition processes is important for understanding the multiple impacts of high-latitude dust (HLD) on the Earth’s systems. Here, we identify, describe, and quantify the source intensity (SI) values, which show the potential of soil surfaces for dust emission scaled to values 0 to 1 concerning globally best productive sources, using the Global Sand and Dust Storms Source Base Map (G-SDS-SBM). This includes 64 HLD sources in our collection for the northern (Alaska, Canada, Denmark, Greenland, Iceland, Svalbard, Sweden, and Russia) and southern (Antarctica and Patagonia) high latitudes. Activity from most of these HLD sources shows seasonal character. It is estimated that high-latitude land areas with higher (SI ≥ 0.5), very high (SI ≥ 0.7), and the highest potential (SI ≥ 0.9) for dust emission cover > 1 670 000 km 2 , > 560 000 km 2 , and > 240 000 km 2 , respectively. In the Arctic HLD region (≥ 60◦ N), land area with SI ≥ 0.5 is 5.5 % (1 035 059 km 2 ), area with SI ≥ 0.7 is 2.3 % (440 804 km 2 ), and area with SI ≥ 0.9 is 1.1 % (208 701 km 2 ). Minimum SI values in the northern HLD region are about 3 orders of magnitude smaller, indicating that the dust sources of this region greatly depend on weather conditions. Our spatial dust source distribution analysis modeling results showed evidence supporting a northern HLD belt, defined as the area north of 50◦ N, with a “transitional HLD-source area” extending at latitudes 50–58◦ N in Eurasia and 50–55◦ N in Canada and a “cold HLD-source area” including areas north of 60◦ N in Eurasia and north of 58◦ N in Canada, with currently “no dust source” area between the HLD and low-latitude dust (LLD) dust belt, except for British Columbia. Using the global atmospheric transport model SILAM, we estimated that 1.0 % of the global dust emission originated from the high-latitude regions. About 57 % of the dust deposition in snow- and ice-covered Arctic regions was from HLD sources. In the southern HLD region, soil surface conditions are favorable for dust emission during the whole year. Climate change can cause a decrease in the duration of snow cover, retreat of glaciers, and an increase in drought, heatwave intensity, and frequency, leading to the increasing frequency of topsoil conditions favorable for dust emission, which increases the probability of dust storms. Our study provides a step forward to improve the representation of HLD in models and to monitor, quantify, and assess the environmental and climate significance of HLD.

high latitude dust↗
NASA NTRS2012

Transport of Alaskan Dust into the Gulf of Alaska and Comparison with Similar High-Latitude Dust Environments

Transport of Alaskan dust into the Gulf of Alaska and comparison with similar high-latitude dust environments. An airborne flux of the micronutrient iron, derived from dust originating from coastal regions may be an important contributor of iron to the Gulf of Alaska's (GoA) oligotrophic waters. Dust blowing off glacier termini and dry riverbeds is a recurring phenomenon in Alaska, usually occurring in the autumn. Since previous studies assumed that dust originating in the deserts of Asia was the largest source of . airborne iron to the GoA, the budget of aeolian deposition of iron needs to be reassessed. Since late 20 I 0, our group has been monitoring dust activity using satellites over the Copper River Delta (CRD) where the most vigorous dust plumes have been observed. Since 2011, sample aerosol concentration and their composition are being collected at Middleton Island (100km off shore of CRD). This presentation will show a summary of the ongoing dust observations and compare with other similar environments (Patagonia, Iceland) by showing case studies. Common features will be highlighted

Crusium, John↗
NASA NTRS2016

High Latitude Dust in the Earth System

Natural dust is often associated with hot, subtropical deserts, but significant dust events have been reported from cold, high latitudes. This review synthesizes current understanding of high-latitude (> or = 50degN and > or = 40degS) dust source geography and dynamics and provides a prospectus for future research on the topic. Although the fundamental processes controlling aeolian dust emissions in high latitudes are essentially the same as in temperate regions, there are additional processes specific to or enhanced in cold regions. These include low temperatures, humidity, strong winds, permafrost and niveo-aeolian processes all of which can affect the efficiency of dust emission and distribution of sediments. Dust deposition at high latitudes can provide nutrients to the marine system, specifically by contributing iron to high-nutrient, low-chlorophyll oceans; it also affects ice albedo and melt rates. There have been no attempts to quantify systematically the expanse, characteristics, or dynamics of high-latitude dust sources. To address this, we identify and compare the main sources and drivers of dust emissions in the Northern (Alaska, Canada, Greenland, and Iceland) and Southern (Antarctica, New Zealand, and Patagonia) Hemispheres. The scarcity of year-round observations and limitations of satellite remote sensing data at high latitudes are discussed. It is estimated that under contemporary conditions high-latitude sources cover >500,000 sq km and contribute at least 80-100 Tg/yr1 of dust to the Earth system (approx. 5% of the global dust budget); both are projected to increase under future climate change scenarios.

albedo↗
NASA NTRS2019

Pixel-Based Model For High Latitude Dust Detection

Dust has implications on the energy budget, ocean biodiversity, and economy at regional and global scales. Dust detection relies on spectral sensitivity at visible (RGB) and infrared wavelengths. Radiative properties of high latitude dust and the background surface albedo in these regions (>40°N, >40°S) complicate current dust detection methods. Leveraging supervised machine learning (ML) methods, we propose a new method accounting for regional differences of dust occurrence.

High latitude dust↗
NASA NTRS2019

Pixel Based Model For High Latitude Dust Detection

Current methods of dust detection rely on spectral sensitivity at visible (RGB) and infrared wavelengths. However, their application on different regions needs to be tuned to mitigate errors associated with background properties. High latitude dust (HLD) regions are characterized by surface with variable albedos and land cover, thus further complicating the dust detection. Leveraging supervised machine learning (ML) methods, we propose a new method accounting for regional differences of dust occurrence.

High latitude dust↗
NASA NTRS1989

Dust emission from high latitude cirrus clouds

In order to study dust emission from grains in the interstellar medium, the infrared properties were analyzed in a number of isolated high latitude dust clouds which contain no dominant internal heating sources. The clouds are spatially resolved, have a simple geometry, and are mapped in the IRAS bands at 12, 25, 60, and 100 microns. For a number of these clouds, extinction data (A sub B) were obtained from starcounts. A large part (30 to 50 percent) of the infrared radiation of the clouds in the IRAS wavelength range of 8 to 130 micron is emitted in the short wavelength bands at 12 and 25 micron. The 60/100 micron ratios for the integrated fluxes of the clouds have a typical value of 0.19 + or - 0.05.

Laureijs, Rene J.↗
NASA NTRS1990

Transport of dust to high northern latitudes in a Martian polar warming

The transport of dust in the Martian atmosphere into high northern latitudes as a result of a Martian polar-warming (and global-dust-storm) event was investigated using a simplified transport model in conjunction with a beta-plane dynamical model to simulate the transport of dust. Numerical experiments were performed to examine the influence of different warming dynamics and to assess the sensitivity of the transport to the initial dust distribution. Results indicate that substantial amounts of dust could be transported and deposited at high northern latitudes (extending to the pole) in a polar-warming event. The potential for the transport of water was also examined through simulations, with results indicating that large amounts of water could be transported to the north polar region in a warming, on the condition that substantial condensation and precipitation do not take place in the subpolar regions. However, the warmth of the Martian atmosphere during global dust storms makes the latter possible.

Barnes, Jeffrey R.↗
NASA NTRS1989

H I and dust in the high latitude dark cloud L1642

The high latitude dark cloud L1642 in the 21 cm H I region was mapped using a 100 m radio telescope. A remarkable H I line broadening from 2.5 to 2.9 km/s is observed over a small area on the bright side of L1642, i.e., the side facing the galactic plane. Results are presented concerning the effects of the asymmetrical UV radiation field of OB stars on the H I gas and the very small dust grains associated with L1642.

Liljestroem, Tarja↗
NASA NTRS1987

Numerical simulations of dust transport into northern high latitudes during a Martian polar warming

The formation and evolution of the polar laminated terrain depends on rates of dust transport to the polar caps. A simplified dynamical model is shown similar to models used to simulate terrestrial stratospheric polar warmings could simulate certain observed features of the circulation during Martian global dust storms. Model simulations of dust transport showed that substantial quantities of dust, enough to produce optical depths of approx. 1, could reach the pole during these storms.

Barnes, J. R.↗
NASA NTRS1989

A rocket-borne measurement of interstellar dust emission at high galactic latitude

The diffuse brightness of the sky was measured in six submillimeter passbands, using a rocket-borne, liquid helium-cooled, absolute radiometer. The average brightness was reported which was observed in each of the passbands, and the dominant source of emission was tentatively identified in the three shortest wavelength bands as interstellar dust (ISD). Spacial structure was observed in these bands, as would be expected for emission from the ISD. The average column density of H I was calculated in each field of view along the scan path. All three bands show a significant correlation with H I. The obtained values are in excellent agreement with those computed for a mixture of graphite and silicate grains. A significant residual emission, not correlated with the H I column density, is evident in all three channels.

Lange, Andrew E.↗
NASA NTRS2003

Determination of Net Martian Polar Dust Flux from MGS-TES Observations

Using atmospheric dust abundance and atmospheric temperature observation data from the Thermal Emission Spectrometer (TES) on board the Mars Global Surveyor (MGS), the net flux of dust into and out of the Martian polar regions will be examined. Mars polar regions possess layered terrain , believed to be comprised of a mixture of ice and dust, with the different layers possibly representing different past climate regimes. These changes in climate may reflect changes in the deposition of dust and volatiles through impacts, volcanism, changes in resources of ice and dust, and response to Milankovitch type cycles (changes in eccentricity of orbit, obliquity and precession of axis). Understanding how rapidly such layers can be generated is an important element to understanding Mars climate history. This study uses the observed vertical temperature data and dust content measurements from TES to analyze the sign (gain or loss) of dust at high latitudes.

M A Blackmon↗
NASA NTRS1975

Windblown dust on Venus

The threshold frictional velocity necessary to initiate grain movement on the Venus surface is 1 to 2 cm/s. Particles smaller than 30 or 40 microns in effective diameter will also be so moved and suspended at the threshold of movement. Theoretical arguments and Venera 8 Doppler measurements suggest marginally that dust should not be raised at the Venera 8 landing site (10 deg S), but should be raised at higher latitudes. Dust carried to tens of kilometers altitude will be transported over the entire planet and may make important contributions to the solar energy deposition, general circulation, and cloud chromosphere problems. However, the Venera 8 photometer measurements and the low albedo of reasonable surface materials imply a clear lower atmosphere at 10 deg S, despite the fact that dust raised at high latitudes should contribute to the aerosol content at this latitude. Dust raising on Venus may be inhibited by limited vertical turbulent diffusion or by thermal sintering of particles on the planetary surface.

Sagan, C.↗
NASA NTRS1989

A faint, dust-enshrouded carbon star at high galactic latitude

During the initial phase of a program to search for substellar candidates at high galactic in the IRAS Serendipitous Survey Catalog, one source, SSC 08546+1732, was found to have no optical couterpart on the Palomar Observatory Sky Survey plates. Ground-based positional, photometric, and spectroscopic observations have identified this source as a heavily dust-enshrouded carbon star, similar to those found in the Galactic plane. The high latitude and relative faintness of this source imply that it lies at a distance of 20-50 kpc, and is 10-30 kpc out of the plane of the Galaxy. SSC 08546+1732 and one other distant obscured carbon star found in the IRAS Point Source Catalog (Low 1987; Beichman et al. 1989) represent the first examples of such objects found in the Galactic halo. These stars may either have evolved from Population I precursors ejected from the disk, or they may be the first obscured Population II halo carbon stars to be observed. A survey for other distant enshrouded carbon stars in the IRAS Faint Source Cattalog should help to elucidate the nature of this new population.

Cutri, Roc M.↗
NASA NTRS1993

Dust near luminous ultraviolet stars

This report describes research activities related to the Infrared Astronomical Satellite (IRAS) sky survey. About 745 luminous stars were examined for the presence of interstellar dust heated by a nearby star. The 'cirrus' discovered by IRAS is thermal radiation from interstellar dust at moderate and high galactic latitudes. The IRAS locates the dust which must (at some level) scatter ultraviolet starlight, although it was expected that thermal emission would be found around virtually every star, most stars shown no detectable emission. And the emission found is not uniform. It is not that the star is embedded in 'an interstellar medium', but rather what is found are discrete clouds that are heated by starlight. An exception is the dearth of clouds near the very hottest stars, implying that the very hottest stars play an active role with respect to destroying or substantially modifying the dust clouds over time. The other possibility is simply that the hottest stars are located in regions lacking in dust, which is counter-intuitive. A bibliography of related journal articles is attached.

Henry, Richard C.↗
NASA NTRS1994

Voyager investigation of the cosmic diffuse background: Observations of rocket-studied locations with Voyager

Attachments to this final report include 2 papers connected with the Voyager work: 'Voyager Observations of Dust Scattering Near the Coalsack Nebula' and 'Search for the Intergalactic Medium'. An appendix of 12 one-page write-ups prepared in connection with another program, UVISI, is also included. The one-page write-ups are: (1) Sky survey of UV point sources to 600 times fainter than previous (TD-1) survey; (2) Diffuse galactic light: starlight scattered from dust at high galactic latitude; (3) Optical properties of interstellar grains; (4) Fluorescence of molecular hydrogen in the interstellar medium; (5) Line emission from hot interstellar medium and/or hot halo of galaxy; (6) Integrated light of distant galaxies in the ultraviolet; (7) Intergalactic far-ultraviolet radiation field; (8) Radiation from recombining intergalactic medium; (9) Radiation from re-heating of intergalactic medium following recombination; (10) Radiation from radiative decay of dark matter candidates (neutrino, etc.); (11) Reflectivity of the asteroids in the Ultraviolet; and (12) Zodiacal light.

Henry, Richard C.↗
NASA NTRS2019

Analysis of the Global Microwave Polarization Data of Clouds

Two NASA microwave radiometers, the satellite-borne GPM (Global Precipitation Measurement) Microwave Imager (GMI) and the aircraft-borne CoSMIR (the Conical Scanning Millimeter-wave Imaging Radiometer), measure vertically- and horizontally-polarized microwaves emitted by cloud particles and the Earth below, providing unique information on ice crystal properties in clouds. Their data reveal that non-spherical ice crystals are common and they fall in a preferred horizontally aligned orientation in convective and optically thick clouds especially near cloud top. A bin (particle-size-resolving) microphysical model with an ice crystal shape representation is developed to simulate the evolution of ice crystal properties (i.e., size, shape and orientation), where the radiation effect on microphysics (REM) is taken into account. Since REM represents the effect of all (e.g., both infrared and solar) radiation on ice crystal temperature, it relies upon the ice crystal proprieties that determine how an ice crystal receives radiation. Definitely, REM is different from the radiative effects that cause sensitivity at the microwave frequencies in the GPM and CoSMIR observations. Model results show that horizontally-oriented ice crystals grow faster than vertically-oriented (or spherical) ones due to REM. When both horizontally- and vertically-oriented ice crystals coexist in an air parcel, the model results show that the former grow by vapor deposition whereas the latter shrink by sublimation and disappear eventually. These modeling results are supported by the GMI data and the CoSMIR observations from MC3E (Midlatitude Continental Convective Clouds Experiment) and OLYMPEX (Olympic Mountains Experiment) on the prevalence of horizontally-oriented ice crystals. Moreover, the REM-induced precipitation explains the CloudSat observations of rare thin clouds in the tropical mid-troposphere as well as the common diamond dust in the high latitudes.

Xiping Zeng↗
NASA NTRS1978

Mariner 9 television limb observations of dust and ice hazes on Mars

Results are presented for a statistical analysis of over 3000 Mariner 9 television reflectance profiles of the planetary limb of Mars for the period from the decaying phase of a global dust storm (southern summer) to southern winter solstice. It is shown that during the decaying phase of the storm, the dust is maintained aloft to high elevations by vertical mixing primarily in the equatorial zone, apparently by the direct or indirect action of the diurnal tide; the result is that the dust decay is much faster in high-latitude regions than near the equator. Significant dust remains aloft in Martian equatorial regions long after the major dust storms have subsided. At the top of the dusty atmosphere, a region exists where temperatures relax toward values expected for a dust-free CO2 atmosphere; this is therefore a region of convective overturning topped by thin condensation hazes resembling terrestrial noctilucent clouds, thereby showing occasionally gravity wave structures.

Anderson, E.↗